Edinburgh, 'cos I went to Uni there. And not because Patrick told me…
I don’t think Scotland can leave Great Britain. How deep a channel would they have to dig before Scotland counted as a separate island?
And St. Davids, of course: Britain’s smallest city (by the British definition of city).
I hope I have this correct-British cities include Scottish cities.
English cities-well that list doesn’t.
So,
Glasgow.
Then Edinburgh because I have visited there.
Dover.
Brighton. I read a book to my grandson last year, and a lot of the action took place in Brighton.
Leeds.
Glasgow, because it’s where I grew up, more or less.
Excluding my home town, York comes to mind for some reason.
Manchester. I’ve seen so many TV shows and movies set there.
EDIT: Funny but I read “British” as “English.” Scotland, Wales and Northern Ireland didn’t even spring to mind.
Ottery St. Catchpole.
No, wait, that’s just a Harry Potter city. It should totally be real, though.
My actual answer is Birmingham.
Brit here – I lived in Peterborough (below), from ages 9 to 19, with interruptions. Frankly, never a bright jewel in Britain’s tourist crown.
There are the real villages of Ottery St. Mary and Venn Ottery, on the River Otter, in East Devon. I get the impression that O. St. C. in the Potter books, where the Weasleys live, is west of London, but not so far west as Devon.
That sounds like Haiti deciding it’s not a part of Hispaniola…
Oxford. Because Morse. 
Skelmersdale, north of Liverpool.
Cities, not obscure hamlets outside villages.
Torquay, because of Agatha Christie. Then Liverpool.
I believe you insulted the 38,000+ people residing there. I’ve been there and it is clearly a city.
Oxford first. Then Cambridge, because Oxford makes me think of elite universities. Then Glasgow because I took a train from Cambridge to Glasgow in 1993. Then Inverness and Tain, because Scotland makes me think of whisky and Tain is home of the Glenmorangie distillery. Then Cardiff, because Doctor Who is filmed there and I realized that the question asked “British,” and I had English and Scottish cites but nothing from Wales.
Aberdyfi in Wales because I’m thinking of Wales now and I remember that Aberdyfi is the real-life location that author Susan Cooper used as the basis for locations in the last two “Dark is Rising” books I read as a kid.
Then Salisbury, because Dark is Rising makes me think of quasi-mystical sites and Stonehenge is near Salisbury.
Then I stopped free-associating and posted.
Does it have a minster or cathedral? If not - not a city.
Croydon. Which does have a minster.
It is not a city, but it is also not a tiny hamlet - I assume the other poster was taking the piss.
Fun facts about Britain’s often obscure practices. We actually have pretty strict definitions about what constitutes are city, rather than a town. It either needs…
- A cathedral, or
- To be granted city status by the Queen. Since 2000, this has been done through a competition on special occasions (eg the millennium celebrations). Brighton & Hove (two towns sandwiched together) applied for and were granted city status at that time, Bath actually took the decision that they did not want to be designated as a city, so chose not to apply. I have no idea what the benefit is either way, beyond calling your town a ‘city’.
I’m from Birmingham, so thought ‘Birmingham’. It’s much bigger than Manchester, but its PR department has always done a terrible job.